The present invention is a method for forming a fiber treating composition comprising contacting an aminofunctional polysiloxane comprising at least one aminofunctional siloxy unit with a mixture comprising a lactone and an alkylsulfate of benzimidazole. The compositions of the present method are especially useful for treating cotton fabrics and blend of cotton and synthetic fiber fabrics to impart good softness and water absorbency and improved whiteness and durability of the treatment.
It is known to treat fibrous materials such as textiles with polysiloxanes to impart desirable properties such as water repellency, lubricity, and crease resistance. It is also known to treat textiles with aminofunctional polydimethylsiloxanes, to provide for textiles having extremely soft hand, however such treatment typically results in a yellowing of the fabric. Czech, U.S. Pat. No. 5,593,611, describes a method for treating a textile to impart amine-like softness and reduced yellowing comprising treating a textile with an aminopolysiloxane having an amine content as --NH.sub.2 ranging from about 0.15 to 0.25 percent by weight as --NH.sub.2 and having a molecular weight of at least about 30,000 However, treatment with such aminofunctional polydimethylsiloxanes while providing for good softness typically cause some yellowing and lost of water absorbency of the treated textile.
Cray et al., U.S. Pat. No. 5,100,991, teach polydiorganosiloxanes having a group described by formula .dbd.NCO(CHR).sub.n OH connected with a silicon atom of a siloxane unit of the polydiorganosiloxane where R represents a hydrogen atom or an alkyl group and n has a value in the range of 2 to 7. Cray et al. teach that such amide substituted polyorganosiloxanes can be made by reaction between lactone and an amino substituted organosilicon compound. Lautenschlager et al., Textile Chemist and Colorist, Vol. 27, No. 3, p.27-29, teach that an aminosilicone partially acylated with butyrolactone when used to treat fabrics provides for improved softness, whiteness, water absorbency, and soil release characteristic for the fabric when compared to the fabric treated with standard aminosilicones.
Alkylsulfates of benzimidazole are known for their use as whiteners in the treatment of synthetic fibers such as acrylics. However, a problem with alkylsufates of benzimidazole is that they are a solid at room temperature, poorly soluble in polysiloxanes, and require a solvent to make them compatible with typical processes for treating fibers. The present inventor has discovered a simple one-step method for preparing amide-functional polysiloxanes in stable mixture with an alkylsulfate of benzimidazole where a portion of the lactone used to solubilize the alkylsulfate of benzimidazole is consumed in the method. The product of the method is an amide-functional polysiloxane in stable admixture with an alkylsulfate of benzimidazole. The product of the method may be used to treat textiles, particularly cotton and cotton-synthetic fiber blends, to provide good softness and water absorbency and improved whiteness and durability compared to those compositions described in the above cited art